This invention relates generally to closure cap constructions, and more particularly to those of a type which are adapted to dispense viscous substances that are characterized by moderate resistance to flow, such as liquid dishwashing detergents or other household items, cosmetic creams or lotions, or for certain food substances, such as syrups, etc.
A number of known dispenser constructions employ a push-pull cap of a type wherein the cap is provided with a discharge orifice, and the cap body with an upstanding stopper plug that is adapted to be received in the discharge orifice when the cap is depressed to a closed, sealing position. In many of these structures, the physical size of the openings through the cap body and around the upstanding stopper plug is restricted to a large degree; this presents little problem where the product contained in the dispenser is of a watery consistency, since the non-viscous nature thereof permits it to flow through the relatively small passages with only minimal resistance.
With substances that are more viscous, however, flow can be severely restricted. In the past, compromises have frequently had to be made; on the one hand it was necessary to keep the physical size of the cap components small, which is important aesthetically, as well as in minimizing the amount of material employed in the molding of each part. On the other hand, consideration had to be given to providing adequate passage widths to permit the desired flow rates to be achieved, while at the same time maintaining the thicknesses of the walls of the cap components adequate to insure sufficient strength and rigidity. Moreover, the molder had to insure that in his design, the plastic substance from which the components was formed was capable of flowing into the mold cavities properly so as to completely fill all of the spaces therein and thereby avoid surface defects in the finished parts.
Attempts to make the cap walls thinner have resulted in structures which were insufficiently stiff or rigid, and which lacked the necessary strength. In addition, the problem noted above, involving proper flow of the plastic into the interstices of the mold cavity, has had to be considered.